Recently CPVC has experienced steady growth in demand as various technologies have emerged relative to physical compound modifications. Improvements have been shown particularly for flow modification applicable to injection molding applications. A variety of melt flow and impact modifiers have been employed in modifying CPVC which have spurred the advancement in molding and performance properties.
Recent disclosures illustrate approaches pertaining to modified CPVC. U.S. Pat. No. 4,847,331 discloses a CPVC compound comprising a blend of CPVC having a chlorine content of between about 60% and 66% by weight and a polymethylmethacrylate comprising not more than 80% by weight of the blend. The composition of matter displays homogeneous, substantially single phase behavior with the CPVC and polymethylmethacrylate being substantially or completely miscible. The resulting blended material exhibits enhanced temperature and durability properties and remains homogeneous up to a temperature of 230.degree. C.
U.S. Pat. No. 4,647,626 discloses a blend of CPVC having chlorine content between 60% and 67% by weight and a styrene-acrylonitrile (SAN) copolymer having acrylonitrile content between 15% and 25%. Partial solubility is presumed from a single glass transition endotherm.
U.S. Pat. No. 4,710,533 discloses a CPVC blend including the aforementioned SAN copolymer and a flow enhancing polymer such as alpha-methyl styrene. Impact modifiers such as ABS are also suggested.
U.S. Pat. No. 4,501,849 discloses a rigid CPVC blend with a high melt flow polypropylene which serves to retard the fusion rate of the CPVC compound during processing.
It was heretofore unknown that certain blends of CPVC and PVC would exhibit a significantly improved combination of properties and that particular blends would exhibit along with the property improvements, sufficient melt flow as to be useful particularly for injection molding of articles. Such a blend would be desirable if the need for employing the aforementioned melt flow and impact modifiers could be reduced or eliminated thereby providing improvements for example in compound simplicity, flame resistance, ease of processing and raw material cost economics.